Rolled inductor with thermal pottant

ABSTRACT

An apparatus includes a substrate layer formed from a pottant material that extends longitudinally in an unwound state. Cores are spaced longitudinally along the substrate layer and joined to the substrate at a first surface. The apparatus further includes pottant segments joined to the cores at a second surface opposite the first surface.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This divisional application claims priority from application Ser. No.14/146,834, filed Jan. 3, 2014, now U.S. Pat. No. 9,496,085, entitledMETHOD OF MANUFACTURING AN INDUCTOR COIL, which is hereby incorporatedby reference.

BACKGROUND

Inductors are known in the art, and are used to resist against changesin current through the coil. Inductors typically include a coil ofconductive material wrapped around a magnetic core. Often, such coresare formed in a closed loop. Known inductors include coils that arewrapped manually, such as by a winding machine. Typically, theinductor's magnetic core and windings are placed between an outer walland an inner wall.

In some applications, inductors dissipate significant quantities ofheat. Because of this, known inductors are potted in heat dissipatingmaterials. The pottant is typically poured between the inner wall andthe outer wall to surround the windings and to provide environmental,thermal, and structural support to the cores and windings. Pottants musthave a high degree of plasticity to fully fill the cavity between thewindings and the outer casing when poured. Furthermore, the pottantselected should have as high of a coefficient of thermal transfer aspossible, in order to maximize heat transfer to the outer casing.

Known pottants attempt to provide both desired rheological attributes(i.e., high plasticity/flowability for pouring) as well as highcoefficients of thermal transfer.

SUMMARY

An apparatus includes a substrate layer formed from a pottant materialthat extends longitudinally in an unwound state. Cores are spacedlongitudinally along the substrate layer and joined to the substrate ata first surface. The apparatus further includes pottant segments joinedto the cores at a second surface opposite the first surface.

Another apparatus includes cores in which each core forms an annularsector that is wrapped with windings. A preformed substrate layer formedfrom pottant material extends longitudinally in an unwound state andcircumscribes the cores in a wound state. The substrate layer furtherincludes recesses corresponding to one of the windings along a radiallyouter surface of one of the cores.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a toroidal inductor that is additivelymanufactured.

FIG. 2A is a cross-sectional view of the toroidal inductor of FIG. 1taken along 2A-2A.

FIG. 2B is a modified view of the toroidal inductor of FIG. 2Aillustrating the insertion of a gap filler.

FIG. 2C is a cross-sectional view of an additive manufacturing processfor manufacturing a toroidal inductor core.

FIG. 3 is a perspective view of an octagonal inductor that is additivelymanufactured.

FIG. 4A is a cross-sectional view of the octagonal inductor of FIG. 3taken along line 4A-4A.

FIG. 4B is an exploded view illustrating the insertion of gap fillersinto an unwrapped octagonal inductor.

FIG. 4C illustrates the wrapping of the octagonal inductor.

FIG. 5A is a perspective view of an additively manufactured end windingstructure.

FIG. 5B is a cross-sectional view of the end winding structure of FIG.5A taken along line 5B-5B.

FIG. 6 is an exploded cross-sectional view of a toroidal inductor thatis not additively manufactured.

FIGS. 7A-7B are flowcharts illustrating methods of creating an inductorcore.

DETAILED DESCRIPTION

An inductor is created by forming cores with windings in a flat layeralong a substrate of a pottant material with a high thermalconductivity, then wrapping the substrate and cores into a loop. Byforming the substrate and cores in layers, for example by additivemanufacturing, windings can be built into a high thermal conductivitypottant surrounding the cores. The high thermal conductivity pottantcompletely surrounds the windings, and can be made of a material thathas a high thermal conductivity without consideration of the material'splasticity or flowability.

FIG. 1 is a perspective view of toroidal inductor 10A. Toroidal inductor10A includes base 12A, inner wall 14A, outer wall 16A, a series of eightcores 18A, eight gap fillers 20A, and pottant 22A.

Base 12A is a structural portion of toroidal inductor 10A. In someembodiments, base 12A may include mounting hardware configured to attachtoroidal inductor 10A to adjacent structures, such as heat sinks or ahousing. Inner wall 14A and outer wall 16A are additional structuralportions of toroidal inductor 10A. Inner wall 14A and outer wall 16A areconfigured to house cores 18A, gap fillers 20A, and pottant 22A. Innerwall 14A and outer wall 16A may be configured to dissipate heat, eitherdirectly or through thermal coupling with a heat sink.

Inner wall 14A and outer wall 16A sit on base 12A. Cores 18A arearranged in the region defined between base 12A, inner wall 14A, andouter wall 16A. Gap fillers 20A are arranged between each adjacent pairof cores 18A. Pottant material 22A is arranged between cores 18A andinner wall 14A, to completely separate cores 18A from inner wall 14A.Pottant material 22A is further arranged between cores 18A and outerwall 16A, to completely separate cores 18A and gap fillers 20A fromouter wall 16A.

Toroidal inductor 10A has eight cores 18A, each of which iscircumscribed by a plurality of windings 24A (FIGS. 2A-2C). In someembodiments, subsets of cores 18A may be associated with each of severalphases. Toroidal inductor 10A may be driven by two- or three-phasepower, for example, each of which would drive the windings surrounding asubset of cores 18A. Gap fillers 20A are arranged between each of cores18A to electrically and magnetically separate the windings 24A (FIGS.2A-2C) surrounding each of cores 18A. Gap fillers 20A are made of adielectric material.

Pottant 22A completely fills the region between cores 18A and inner andouter walls 14A and 16A, respectively. Windings 24A are encapsulated bypottant 22A, as shown in more detail with respect to FIGS. 2A-2C.Pottant 22A facilitates heat transfer from cores 18A and windings 24A(FIGS. 2A-2C) to inner wall 14A and outer wall 16A, where it may bedissipated. Pottant 22A has a high thermal conductivity, exceeding 17W/m-K.

FIG. 2A is a cross-sectional view of toroidal inductor 10A of FIG. 1A,taken along 2A-2A. FIG. 2A illustrates inner wall 14A, outer wall 16A,cores 18A, gap fillers 20A, and pottant 22A, as previously describedwith respect to FIG. 1A. Furthermore, FIG. 2A illustrates windings 24Aembedded within pottant 22A. As shown in FIG. 2A, eleven windings 24Apass through pottant 22A radially outward of core 18A, and elevenwindings 24A pass through pottant 22A radially outward of core 18A.

Windings 24A are electrically interconnected; for example, all elevenwindings 24A associated with each core 18A are electrically connected.Windings 24A form coils around each of cores 18A, such that whenelectric current is driven through windings 24A, a magnetic field isgenerated through cores 18A. Windings 24A associated with each of cores18A may be either electrically isolated or connected from one another.For example, in some embodiments, multiple phases of electric currentare each associated with a subset of cores 18A. In other embodiments,for example those driven by a single-phase DC voltage source, all ofwindings 24A may be electrically interconnected.

As shown in FIG. 2A, windings 24A are circumferentially evenly spaced,radially outward of cores 18A. Windings 24A are staggered radially intotwo evenly spaced circumferential rows radially inward of cores 18A. Inother embodiments, various other configurations of windings 24A arepossible. It is often desirable to disperse windings 24A throughoutpottant 22A such that heat generated as a result of driving currentthrough windings 24A is transferred efficiently to pottant 22A.

FIG. 2B is a modified view of toroidal inductor 10A. Toroidal inductor10A of FIG. 2B includes substantially the same components as thosepreviously described. However, in FIG. 2B, inner wall 14A and outer wall16A have been omitted to illustrate toroidal inductor 10A in itsunwrapped state. FIG. 2B illustrates a layerwise construction oftoroidal inductor 10A.

Toroidal inductor 10A can be formed in an unwrapped condition. Toroidalinductor 10A of FIG. 2B includes the same components as previouslydescribed, and further illustrates substrate layer 26A (including flatportions 28A and arcs 30A), core layer 32A, and inner layer 34A(comprised of eight segments 36A) prior to being wound into a closedloop.

Substrate layer 26A is a series of eight arcs 30A comprised primarily ofpottant material 22A. Each of the arcs 30A further includes elevenevenly spaced windings 24A. Between each of the arcs 30A is a flatsection 28A. Core layer 32A is formed adjacent to substrate layer 26A.Core layer 32A includes eight cores 18A, each of which are disposedadjacent to one of arcs 30A. Flat sections 28A are left uncovered bycores 18A. Inner layer 34A is formed adjacent to core layer 32A and,like substrate layer 26A, is comprised of windings 24A dispersed amidstpottant material 22A. Inner layer 34A comprises eight separate segments36A of pottant 22A, each including eleven windings 24A. Each segment 36Aof inner layer 34A is disconnected from the other, and each segment 36Ais arranged on an opposite distal end of one of cores 18A from substratelayer 26A.

Gap filler 20A is shown being inserted between two segments 36A towardsa flat section 28A of substrate layer 26A. Gap fillers 20A are insertedbetween each segment 36A and divide adjacent cores 18A and adjacentsegments 36A. When gap fillers 20A have been inserted between each ofcores 18A, toroidal inductor 10A can be wrapped from its unwound state(as shown in FIG. 2B) into a loop and inserted between inner wall 14Aand outer wall 16A (as shown in FIG. 2A).

FIG. 2C is a cross-sectional view of toroidal inductor 10A showing onecore 18A being constructed via an additive manufacturing process. Manyvarieties of additive manufacturing are known to those of skill in theart, including direct metal laser sintering, laser powder sintering,e-beam melting, and laser-object manufacturing, and it is unnecessary toexplain these processes in detail.

It is relatively simple to additively manufacture windings 24A withinpottant 22A by additively manufacturing those components. As shown inFIG. 2C, core 18A, pottant 22A, and windings 24A are additivelymanufactured. Strata of additively manufactured layers are visiblethroughout core 18A, pottant 22A, and windings 24A. Pottant 22A is builtup on base 38A, which is contoured to generate a desired geometry ofpottant 22A such that it will nest inside of outer wall 16A (FIG. 2A).Windings 24A are built in to pottant 22A in a desired orientation. Core18A is additively manufactured adjacent to pottant 22A.

Each of cores 18A, pottant 22A, and windings 24A are additivelymanufactured by depositing pulverant material 40A in layers, thenselectively sintering portions of those layers. Radiation source 42Aproduces a radiation beam 44A, which is directed towards portions ofpulverant material 40A to solidify those portions and form toroidalinductor 10A. Because core 18A, pottant 22A, and windings 24A arecomprised of different materials, pulverant material 40A may becomprised of different materials at different locations. For example,pulverant material 40A may be comprised of a high thermal conductivitymaterial to form pottant 22A, a conductor to form windings 24A, and amagnetic material to form core 18A.

Many portions of toroidal inductor 10A benefit from being additivelymanufactured. Additive manufacturing allows for any placement ofwindings 24A within pottant 22A. The placement of windings 24A may bechosen to facilitate thermal transfer from windings 24A through pottant22A. Furthermore, additively manufacturing pottant 22A, rather thanpouring or injecting a pottant material into an otherwise-completeinductor, allows for the selection of a pottant material that need notbe flowable or pourable. Thus, pottant 22A may be selected from a largercategory of materials having higher thermal conductivity.

FIG. 3 is a perspective view of octagonal inductor 10B. Octagonalinductor 10B is similar to toroidal inductor 1A of FIG. 1, in that itincludes base 12B, inner wall 14B, outer wall 16B, cores 18B, gapfillers 20B, and pottant 22B, which are substantially similar infunction to their counterparts in toroidal inductor 10A. However, cores18B of FIG. 3 are shaped as polygons such that, when combined with gapfillers 20B, octagonal inductor 10B has a substantially octagonalcross-sectional profile. Accordingly, inner wall 14B and outer wall 16Bare octagonal to contain the octagonal combination of cores 18B gapfillers 20B.

FIG. 3 illustrates just one way in which inductors can be formed thathave a non-toroidal shape. In alternative embodiments to those shown inFIGS. 1A and 1B, inductors can be formed having various geometries. Forexample, hexagonal inductors can be created, or inductors having apolygonal outside wall and a circular inner wall. Because of the processused to form these inductors, described in more detail below, virtuallyany combination of shapes of inner wall 14B and outer wall 16B ispossible.

FIG. 4A is a cross-sectional view of octagonal inductor 10B of FIG. 3,taken along line 4A-4A. Octagonal inductor 10B is similar to toroidalinductor 10A of FIGS. 1 and 2A-2C. However, cores 18B of octagonalinductor 10B are polygonal, so that octagonally shaped inner wall 14Band outer wall 16B circumscribe cores 18B, gap fillers 20B, pottant 22B,and windings 24B.

FIG. 4B is a modified view of octagonal inductor 10B of FIG. 4A, in anunwound state. FIG. 4B shows the insertion of gap fillers 20B beinginserted into flat sections 28B along substrate 26B, which includespottant material 22B and windings 24B. Gap fillers 20B separate each ofcores 18B along core layer 32B. Inner layer 34B comprises eight segments36B, each of which includes pottant material 22B surrounding windings24B. Unlike toroidal inductor 10A, octagonal inductor 10B does not havearcs 30A (FIG. 2B).

The straight-lined, polygonal shape of cores 18B is simple tomanufacture and roll into a loop, as is described in more detail withrespect to FIG. 4C. Octagonal inductor 10B can be additivelymanufactured without a shaped substrate (e.g., base 38A of FIG. 2C).

FIG. 4C illustrates the rolling process for wrapping octagonal inductor10B into a loop. Starting from the unwound condition shown in FIG. 4B,octagonal inductor 10B is wrapped as indicated by the arrow. As a resultof the winding of octagonal inductor 10B, gap fillers 20B are positionedimmediately adjacent to both adjacent cores 18B along flat sections 28B.Substrate 26B is bent to approximate an octagonal shape thatapproximates that of outer wall 16B (FIG. 4A). The rolling method toform wound octagonal inductor 10B can be applied to other embodiments,including toroidal inductor 10A (FIGS. 1, 2A-2C).

FIG. 5A is a perspective view of an end winding structure. In theembodiment shown in FIG. 5A, end windings 24 extend from pottantmaterial 22 associated with substrate 26 to pottant material 22associated with section 36. As will be appreciated by those of skill inthe art, end windings 24 interconnect the windings of an inductor coilto generate a magnetic field through core 18. For example, end windings24 could be used to interconnect windings 24A of FIGS. 1 and 2A-2C, oralternatively to interconnect windings 24B of FIG. 3.

In order to show windings 24, FIG. 5A does not show any materialsurrounding windings 24. In most embodiments, a pottant surrounds endwindings 24, so that end windings 24A can dissipate heat, and also toprevent unwanted electrical contact between adjacent end windings 24.

FIG. 5B is a cross-sectional view of the end winding structure of FIG.5A, taken along line 5B-5B. In the view shown in FIG. 5B, thesurrounding insulating material 22 is shown between end windings 24(unlike FIG. 5A, in which a portion of insulating material 22 wasomitted to more clearly show end windings 24). End windings 24 arearranged at a distance from one another to prevent unwanted electricalcontact.

FIG. 6 is an exploded view of inductor 10C, which is not additivelymanufactured. Inductor 10C includes cores 18C, gap fillers 20C, pottantmaterial 22C, and windings 24C. Substrate 26C is made of pottantmaterial 22C, and includes recesses 46C corresponding to the positionsof windings 24C along a radially outer edge of cores 18C. Segments 36Cof FIG. 6 include pottant material 22C, which is a high thermal transfermaterial, arranged along the radially inner distal edge of each of cores18C. Windings 24C are wrapped around cores 18C manually, for example viaan automated winding machine. Recesses 46C are aligned with thepositions of windings 24C, so that efficient thermal transfer isaccomplished.

Pottant material 22C is arranged along both radially inner and outerdistal ends of cores 18C. Substrate 26C is wrapped about the outerradial end of core 18C using the rolling technique discussed previouslywith respect to FIG. 4C. Cores 18C are pre-wrapped with windings 24C,and the resulting structure is placed onto substrate 26C, aligned withrecesses 46C. Segments 36C are placed on a radially inner edge of cores18C. Each of segments 36C also includes recesses 46C, which are alignedto snugly fit with windings 24C, as shown in the exploded view.

Because pottant material 22C is pre-formed to mate with windings 24Csurrounding cores 18C, pottant material 22C need not be flowable orpourable. Thus, pottant material 22C may be selected from materialshaving high thermal conductivity without regard to rheologicalcharacteristics such as pourability or flowability. For example, thethermal conductivity of pottant material 22C may exceed 17 W/m-K.

FIG. 7A is a method of forming an inductor. According to the method ofFIG. 7A, an inductor is made using additive manufacturing.

At step 48, a substrate pottant is formed. The substrate pottant is madeof a material with a high coefficient of thermal conductivity. In oneembodiment, the coefficient of thermal conductivity exceeds 17 W/m-K.The substrate pottant includes windings, which are embedded within thepottant. The substrate can be formed by additive manufacturing to allowfor placement of the windings directly in the pottant material. In thisway, heat may be efficiently transferred from the windings. Thesubstrate pottant may be curved (e.g., substrate 26A of FIG. 2B), flat(e.g., substrate 26B of FIG. 3B), or any other desired geometry to fitwithin an outer wall of a housing of the inductor when rolled into aloop.

At step 50, cores are formed on the substrate. Cores are typically madeof a magnetic material. The cores may also be additively manufactured.The cores are spaced from one another along the substrate by a flatportion.

At step 52, segments are formed on the cores. The segments are made ofpottant material containing built-in windings, much like the substrate.The segments are arranged along an opposite edge of each of the coresfrom the substrate. One segment is formed on each of the cores.

At step 54, gap fillers are placed between each of the cores. The gapfillers are placed on the flat sections of the substrate, in betweeneach adjacent pair of cores. The gap fillers are formed of an insulatingmaterial, and may be manually placed, rather than additivelymanufactured.

At step 56, the cores are wrapped into an inductor coil. The inductorcoil is full loop of cores separated by gap fillers. Around the outsideedge of the loop is the substrate, and along the inner edge are thesegments separated by gap fillers. Optionally, the wrapped inductor coilcan be inserted between an inner wall and an outer wall.

FIG. 7B is a flowchart for a method of forming an inductor core. Themethod shown in FIG. 5B need not include using additive manufacturing toform the components.

At step 58, an outer pottant is formed. The outer pottant need notinclude windings, but may include recesses configured to receivewindings on an adjacent component, as described in more detail below.The pottant is formed from a material having a high coefficient ofthermal transfer.

At step 60, cores are formed. The cores are made of a magnetic material.

At step 62, windings are wrapped on to the cores. Typically, there aremultiple windings on each core. The windings are wrapped such that whencurrent is driven through the windings, a magnetic field is generated inthe magnetic material that makes up the cores. The windings around eachcore may be electrically connected to one another. For example, wherethe desired inductor is driven by a single phase DC voltage source, allof the windings may be electrically connected to one another. Inalternative embodiments, such as those for inductors driven bymulti-phase power sources, subsets of the windings may be electricallyconnected to one another, but not connected to the windings of othercores.

At step 64, the cores are arranged on the outer pottant. The recesses ofthe outer pottant are aligned to engage with the windings surroundingthe cores. In this way, heat can be efficiently dissipated from thewindings via the outer pottant.

At step 66, inner pottant is arranged on the cores. Much like the outerpottant, the inner pottant is formed into a shape that includes recessesconfigured to engage with a portion of the windings surrounding thecores.

At step 68, gap fillers are placed between the cores. The gap fillersare typically formed of an insulating material. The gap fillers and thecores combine to substantially cover one surface of the outer pottantmaterial.

At step 70, the cores are wrapped into an inductor coil. When wrapped,the cores and the segments abut the gap fillers. Furthermore, thewrapped inductor coil is configured to fit between an outer wall and aninner wall of an inductor housing. The wrapped inductor coil is a closedloop, and may have a toroidal or octagonal cross-section.

While the invention has been described with reference to an exemplaryembodiment(s), it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment(s) disclosed, but that theinvention will include all embodiments falling within the scope of theappended claims.

The invention claimed is:
 1. An apparatus comprising: a substrate layerformed from a pottant material that extends longitudinally in an unwoundstate; a plurality of cores spaced longitudinally along the substratelayer, each core having a first surface joined to the substrate layerand a second surface opposite the first surface; and a plurality ofsegments formed from the pottant material, wherein each of the pluralityof segments is joined to one of the plurality of cores along the secondsurface of the core.
 2. The apparatus of claim 1, and furthercomprising: a first plurality of windings embedded within the substratelayer; and a second plurality of windings embedded within the pluralityof segments; wherein the first and second pluralities of windings arearranged in groups, each group of first and second pluralities ofwindings associated with one of the plurality of cores.
 3. The apparatusof claim 2, and further comprising: a plurality of end windingselectrically connecting the first plurality of windings to the secondplurality of windings.
 4. The apparatus of claim 1, and furthercomprising: a plurality of gap fillers, each gap filler disposed betweenadjacent cores and composed of a dielectric material.
 5. The apparatusof claim 4, wherein the plurality of gap fillers abut the plurality ofcores and the plurality of segments in a wound state to form a loop. 6.The apparatus of claim 4, wherein the substrate layer comprises: aplurality of arc portions; and a plurality of flat portions interposedbetween adjacent arc portions.
 7. The apparatus of claim 6, wherein eachof the plurality of cores mates with one of the plurality of arcportions, and wherein each of the plurality of gap fillers mates withone of the flat portions.
 8. The apparatus of claim 1, wherein each ofthe plurality of cores has third and fourth surfaces extending from thefirst surface to the second surface, and wherein the third surface isangled towards the fourth surface at the second surface.
 9. Theapparatus of claim 8, wherein an included angle between the third andfourth surface of each core is substantially equal, the sum of theincluded angles being substantially equal to 360 degrees.
 10. Theapparatus of claim 1, wherein each of the plurality of cores has apolygonal shape.
 11. The apparatus of claim 1, wherein the first surfaceis defined by a first radius, and the second surface is defined by asecond radius concentric with the first radius.